Camera with electrical controls for different types of objectives

ABSTRACT

A camera capable of automatically determining the exposure time and having interchangeable objectives. One of the factors which determines the extent of exposure is the magnitude of the aperture through which light enters the camera. This factor is introduced either by way of one variable resistor which coacts with an objective which remains wide open and which is automatically stopped down to a preselected aperture just prior to exposure, or by way of a second variable resistor adapted to be used in the situation where the objective is not automatically stopped down just prior to exposure and instead has its diaphragm in a stopped down condition restricting travel of light passing through the objective with this light being measured after passing through the stopped down diaphragm. These variable resistors are connected in parallel and a selecting switch is provided for utilizing one or the other of the variable resistors depending upon the type of objective which is used.

United States Patent [191 Miyakawa et al.

m] 3,839,722 1 Oct. 1,1974

[ CAMERA WITH ELECTRICAL CONTROLS FOR DTFFERENT TYPES OF OBJECTIVES [73]Assignee: Asahi Kogaku Kogyo Kabushiki Kaisha, Tokyo-to, Japan [22]Filed: Apr. 23, 1973 [21] Appl. No.: 353,886

Related US. Application Data [62] Division of Ser. No. 251,721, May 9,1972.

[30] Foreign Application Priority Data May 14, 1971 Japan 46-38182 May19, 1971 Japan 46-39719 [52] US. Cl 354/24, 354/46, 354/47,

[51] Int. Cl. G03b 7/00 [58] Field of Search 95/10 C [56] I ReferencesCited UNITED STATES PATENTS 3,515,045 6/1970 Uno 95/10 C 3,587,4216/1971 Ono et a1. 95/10 C Primary Examiner-Samuel S. Matthews AssistantExaminerRussell E. Adams, Jr. Attorney, Agent, or FirmSteinberg & Blake[5 1 ABSTRACT A camera capable of automatically determining the exposuretime and having interchangeable objectives. One of the factors whichdetermines the extent of exposure is the magnitude of the aperturethrough which light enters the camera. This factor is introduced eitherby way of one variable resistor which coacts with an objective whichremains wide open and which is automatically stopped down to apreselected aperture just prior to exposure, or by way of a secondvariable resistor adapted to be used in the situation where theobjective isnot automatically stopped down just prior to exposure andinstead has its diaphragm in a stopped down condition restricting travelof light passing through the objective with this light being measuredafter passing through the stopped down diaphragm. These variableresistors are connected in parallel and a selecting switch is providedfor utilizing one or the other of the variable resistors depending uponthe type of objective which is used.

9 Claims, 4 Drawing Figures PATENTEUBBT 4 I saw sat a hi 5 m @K W mm mmM 9 mm mm CROSS-REFERENCE TO RELATED APPLICATION This application is adivision of copending application Ser. No. 251,721, filed May 9, 1972,and entitled, ELECTRICALLY CONTROLLED PHOTO- GRAPI-IIC CAMERA SHUTTERAPPARATUS.

BACKGROUND OF THE INVENTION brought about in response toexposure-determining factors among which are such factors as thelighting conditions, the size of the aperture through which the exposureis made, and the speed of. the film.

It is known to determine the factor according to the lighting conditionsby measuring light traveling from the object to be photographed throughthe camera objective, after the light has passed through the objective,so that influence of the objective itself on the light is taken intoconsideration in the measurement thereof.

When using a camera of this latter type, there are two basicallydifferent types of objectives which are available with cameras which canaccept interchangeable objectives, such as single lens reflex cameras.Thus, one very well known type of objective is a so-called automaticobjective which enables the object to be photographed and the light tobe measured while the diaphragm is wide open. With an objective of thistype the diaphragm setting ring is set to provide a preselected aperturewhich is automatically achieved by automatic stopping down of thediaphragm just prior to exposure. However, 'such cameras also usenonautomatic objectives which'must be manually stopped down to theaperture which will give a proper exposure, and when it is necessary tomeasure light which travels through such a stopped down diaphragmproblems are encountered with conventional cameras. Thus, the factor ofthe size of the exposure aperture must be added to a factor such as thelighting conditions in order to determine the proper exposure, and theaddition of these factors creates problems where objectives of the abovetwo basic types are interchangeably used.

SUMMARY OF THE INVENTION It is accordingly a primary object of thepresent invention to provide a camera of the above general type whichwill avoid the above problems.

Thus, one of the objects of the present invention is to provide a cameraof the above type with the possibility of using either an automaticobjective where the diaphragm aperture is preselected with automaticstopping down takingplace just prior to exposure or a nonautomaticobjective where the diaphragm is manually stopped down so that light ismeasured while traveling through the stopped down diaphragm.

In particular, it is an object of the invention to provide the circuitryof the camera with structure which will enable the factor of the size ofthe exposure aperture to be utilized in determination of the extent ofexposure with either of these different types of objectives.

According to the invention the camera is provided with circuitry forautomatically determining the extent to which film in the camera isexposed, and this circuitry includes a circuit for providing a signalaccording to the mangitude of the exposure aperture. This latter circuitcomprises a first variable resistor means for introducing a signalaccording to a preselected diaphragm setting when using an objectivewhich has a wide open aperture which is automatically stopped down tothe preselected aperture just prior to exposure. This circuit furtherincludes a second variable resistor means for introducing a signalaccording to the magnitude of the exposure aperture when using anobjective which is not automatically stopped down to a preselectedaperture, so that with the latter objective light measured after passingtherethrough is restricted by the stopped down aperture. These first andsecond variable resistor means are connected in parallel with each otherand respectively include electrically conductive adjustable componentsfor determining the settings of the first and second variable resistormeans. A switch means is operatively connected with the lattercomponents for selectively connecting one or the other of thesecomponents to the circuitry.

BRIEF DESCRIPTION OF DRAWINGS The invention is illustrated by way ofexample in the FIG. 4 is a fragmentary wiring diagram of a differentembodiment of circuitry for introducing the factor of aperture size.

DESCRIPTION OF PREFERRED EMBODIMENTS Referring to FIG. 1, the circuitryillustrated therein for determining the extent to which film in thecamera is exposed includes a DC-DC converter 1 having an input terminalla electrically connected by way of a conductor 30 to a DCvoltage'source formed by the battery 17, this connection to the voltagesource being provided by way of a main switch 16. By way of terminals lband 1c, the converter 1 is connected to a circuit means 5 which servesto introduce into the circuitry exposure-determining factors of the sizeof the exposure aperture and the speed of the film. This circuit means 5is described in greater detail below. However, it will be seen that thecircuit means 5 includes several variable resistor means which areconnected in parallel. As illustrated in FIG. 1 the circuit means 5 issupplied directly from the converter 1, and this arrangement is providedbecause the current consumed by the circuit means 5 remainssubstantially constant.

Two additional circuits are energized with the outpu of the converter 1,and these two additional circuits have a variable current demand, sothat in this case a constant voltage supply means formed by voltageregulators 6 and 7 is used, these voltage regulators also serving tocompensate for thermalvariations. Thus, by way of the output terminal1d, the converter 1 is electrically connected to the voltage regulator6, while by way of the output terminal Ie, the converter 1 iselectrically connected to the voltage regulator 7. These regulators aswell as the converter itself are suitably grounded, as illustrated inFIG. 1. Thus, the DC-DC converter 1 provides a circuit power source forthe circuit 5, this latter power source being independent of the powersource from the battery 17 which is somewhat increased or decreased toachieve output stability at the voltage regulators 6 and 7.

The circuit which is supplied from the voltage regulator 6 is alight-responsive circuit for converting the lighting conditions of theobjective to be photographed into a corresponding electrical signal.This lightresponsive means which is supplied by the voltage regulator 6includes a photosensitive element 3 which receives light from the objectto be photographed, this light first traveling through the objective ofthe camera before reaching the photosensitive means or element 3. Alsothe light-responsive means includes a diode 4 connected in series withthe photosensitive element 3 and acting as a logarithmic compressionelement.

The circuit which is supplied from the voltage regulator 7 is asignal-transmission means formed by the memory capacitor 9 which ischarged to an extent corresponding to the exposure-determining factors,and between the signal-transmission means 9 and the voltage regulator 7there is a logarithmic expansion circuit 8. This latter circuit isnormally grounded through the switch 10. This switch 10 is normallyclosed. When the shutter is opened, however, through an unillustratedmechanism the switch 10 is opened in synchronism with the opening of theshutter, so that the logarithmic expansion circuit 8 is at this timedisconnected from ground and is instead connected in series with thememory capacitor 9, upon opening of the shutter.

The several exposure-determining factors, namely the lightingconditions, the exposure aperture magnitude, and the film speed, areadded by the circuit whose output current charges the capacitor 9through the normally closed switch 11 until the terminal voltage of thecapacitor 9 attains the voltage level of the output from the circuit 5,this charging operation taking place while the switches 10 and 11 remainclosed. When the tiltable mirror of the single lens reflex camera snapsupwardly beyond the path of light traveling along the optical axisthrough the objective, immediately prior to opening of the shutter, theswitch 11 simultaneously opens, with the switch 10 also openingsimultaneously with the opening of the shutter, as referred to above, sothat the charging of the signal-transmission means 9 with the signals tobe used in determining the exposure continues from the time when thecamera is directed toward the object to be photographed (actually fromthe time when the main switch 16 is closed) until the time when theswitch 11 opens.

The junction between the switch 11 and the signaltransmission means 9and a switching circuit means 12, referred to in greater detail below,are interconnected by way of a resistor 9a, so that through thisresistor the signal-transmission means 9 is connected with the switchingcircuit means 12. An indicating means 13, in the form of a suitablemeter, is connected in parallel with the switching circuit means 12. Theswitching circuit means 12 has at its output a transistor 14 which isconnected at its base to the remainder of the switching circuit means12, and through the transistor 14 the switching circuit means 12 isconnected to the voltage source 17 through a circuit which is thuscontrolled by the transistor 14. This latter circuit includes not onlythe energizing source 17 but also the main switch 16, which isautomatically closed during the initial increment of movement of theshutter-tripping plunger, before the shutter is actually tripped, aswitch 15 connected in series with the switch 16 and automaticallyclosed in a known way just prior to opening of the shutter as the mirroris snapped upwardly, and an electromagnetic means 2 which is connectedin series between the transistor 14 and the switch 15. Thiselectromagnetic means 2, when it is deenergized, will in a known wayrelease a trailing curtain of the shutter so that the trailing curtainwill run down to its rest position for closing the shutter. Thus, theelectromagnetic means 2, the switch 15, and the switch 16 are connectedin series between the transistor 14 and the battery 17.

The circuit 5 for adding the exposure-determining factors includes threevariable resistor means 19, 20, and 21. These three variable resistormeans are connected in parallel between the terminals 1b and 1c of theconverter 1. It will be noted that the lightresponsive means formed bythe circuit which includes the components 3 and 4 is connected from thejunction 32 between the components 3 and 4 through a changeover switchmeans 18 to one or the other of the variable resistor means 19 and 20,so that in this way the exposure-determining factor of the lightingconditions at the object to be photographed is added to the otherfactors of the magnitude of the exposure aperture and the film speed,these three factors forming when added together the signal which issupplied to the signal-transmission means formed by the memory capacitor9. Thus, the signal according to the lighting conditions is added, inthe position of the parts shown in FIG. 1, by way of the switch 18 tothe aperture magnitude signal derived from the variable resistor 20which is connected in parallel with the variable resistor means 21 whichprovides the film speed signal, so that these three signals are combinedto form the output of the circuit 5 which is delivered to the capacitor9 while energizing takes place by way of the independent constantvoltage from the converter 1. The magnitude of the signals will dependupon the intensity of the light received by the photosensitive element 3as well as the positions of the movable electrically conductivecomponents of the variable resistor means 20 and 21. In this way thecharging of the memory capacitor 9 is regulated in accordance with theexposure-determining factors.

The variable resistor means 20 is in the form of a potentiometer havinga slidable contact which forms the electrically conductive componentconnected to the switch 18 in the position of the parts shown in FIG. 1.

This variable resistor means 20 is adapted to be used with an objectivewhich is automatic in the sense that it remains wide open and isautomatically stopped down to a preselected aperture just prior toexposure. Such objectives are well known. The objective has an aperturesetting ring which is turned to set the diaphragm for providing apredetermined aperture just prior to exposure. When this ring is turnedthrough an unillustrated transmission the slider of the potentiometer 20is shifted along the potentiometer to introduce into the circuit thefactor of the size of the exposure aperture. The sliding contact of thepotentiometer 21 is moved in the same way by way of a ring which is usedto introduce into the camera a value corresponding to the speed of thefilm which is exposed. In this way the variable resistor means 21 willintroduce a signal according to the film speed. The voltage controlfunction achieved with these potentiometers and 21 is such that avariation of the preselected lens aperture value corresponding to onegraduation of the diaphragm setting ring and a variation of the filmspeed value corresponding to one graduation of the speed setting ringare maintained in correspondence with a variation of the light intensityby one incremental value such as one light value. Therefore, the outputof the circuit 5 is a voltage corresponding to the added informationderived from the light intensity at the object to be photographed, thepreselected aperture magnitude, and the film speed.

The diaphgram setting ring will, as is well known, determine the size ofthe aperture through which the film is actually exposed. However, thisring does not actually stop the diaphragm down to a positioncorresponding to the setting of the ring. This latter stopping down ofthe diaphragm is brought about automatically just priorto exposure, aspointed out above. For this purpose the diaphragm setting ring of suchan automatic objective is coupled to the sliding contact of thepotentiometer 20 in such a way that a pawl or other motiontransmittingelement which moves together with the diaphragm setting ring extendsfrom the lens barrel of the objective into the interior of the camerahousing to transmit the motion to the sliding contact of thepotentiometer 20. Thus, in order to obtain this type of coupledoperation an automatic objective has a special structure fortransmitting the motion from the diaphragm setting ring to thepotentiometer.

However, it is also possible to use with a camera such as a single lensreflex camera a single stage lens which is commercially available andwhich must be manually stopped down to the required aperture since suchlenses do not have motion-transmitting elements which extend into thecamerafor preliminarily setting a potentiometer to a setting whichcorresponds to a selected aperture. Whensuch a non-automatic, manuallyadjustable objective is used with the camera, measurement of the lightwhich travels through the objective takes place in a restricted mannerthrough an aperture which has already been stopped down to the selectedvalue. During light measurement through such a stopped down aperture, itis not possible to obtain a useful function from the potentiometer 20and if the potentiometer 20 is used in determining the extent ofexposure there will be an unavoidable error, this error occurring ofcourse in the light measurement.

In the example shown in FIG. 1, the changeover switch means 18 normallyassumes a position engaging the contact 18b of the adjustable componentof the potentiometer or variable resistor means 19. The projection fromthe automatic objective, when the latter is mounted on the camera,serves not only to transmit movement from the diaphragm setting ring tothe adjustable component of the variable resistor means 20, but also todisplace the switch 18 to the position shown in FIG. 1 where it engagesthe contact 18a of the adjustable component of the variable resistormeans 20. Therefore, when using a non-automatic objective which mustbemanually stopped down, the information or signal with respect to thelight intensity is added, to the variable resistor 19. This secondvariable resistor means 19 has its movable adjusting component fixed bythe manufacturer after displacement to a position establishing acondition according to which the resistance value provided by way of thepotentiometer or variable resistor means 19 corresponds to theresistance which would be derived from the potentiometer 20 with thelatter short-circuited or bypassed.

In this connection, such a circuit arrangement is shown in theembodiment illustrated in FIG. 4 which differs from that of FIG. 1 onlyin that the potentiometer or variable resistor means 20 is indeedprovided with such a bypass switch means 22, as referred to above. Thus,it will be seen from FIG. 4, that the bypass switch means 22 isconnected between the potentiometer 20 and the slidable contact thereof,so that when the switch 22 is closed the potentiometer is bypassed insuch a way that it achieves a constant voltage control functionirrespective of the position of the sliding contact. This switch 22 is anormally closed switch. The motion-transmitting element carried by theautomatic objective will act on this switch 22 in order to open it onlywhen such an automatic objective is used. Therefore a manuallyadjustable objective, which is to say an objective which must have itsdiaphragm manually stopped down, will not influence the switch 22 whichthus remains closed when using such an objective. Therefore in theclosed position of the switch 22 the potentiometer 20 provides aconstant voltage control function irrespective of the position of itssliding contact. The resistance value achieved from the potentiometer 20at this time corresponds to that which is achieved from thepotentiometer 19 when its slidable contact is fixed by the manufacturer.This potentiometer 19 is useful in measuring the light even through anautomatic objective when the-latter is in a condition where itsdiaphragm is actually stopped down.

Thus, with the above structure of FIGS. 1 and 4, when the change-overswitch means 18 engages the contact 18a, light measurement is madethrough a wide open objective with the diaphragm setting beingpreselected but not actually achieved until automatic stopping downtakes place just prior to exposure. On the other hand, when thechange-over switch means 18 engages the contact 18b, it connects intothe circuit the variable resistor means which is adapted to cooperatewith an objective which must be manually stopped down with lightmeasurement taking place through the restriction provided by the stoppeddown diaphragm. Of course, this type of operation is also effective evenwith an automatic objective after the diaphragm thereof is stopped down.It is to be noted that when the switch means 18 engages the contact 18b,the potentiometer 20 is disenabled even if the switch 22 is opened,

so that it is indeed possible to carry out light measurement through astopped down objective even if this objective is of the type whichnormally is automatically stopped down just prior to exposure. In otherwords it may sometimes happen that an automatic objective is used insuch a way that its diaphragm is already in a stop-down condition duringmeasurement of light, and even in this case the circuitry of FIGS. 1 and4 will operate properly.

Thus, the exposure-determining factors supplied to the circuitry throughthe above-described signal supply means are stored in the form of anelectrical charge in the signal-transmission means formed by thecapacitor 9, and this capacitor 9 will temporarily hold this chargesince the switch 11 is opened immediately before the tiltable mirror issnapped upwardly. More specifically, any rays of light which happen topass through the objective after the mirror has snapped upwardly willnot reach the photosensitive element 3 so that the signal informationstored by the capacitor 9 is effectively prevented from being disturbedby signals which otherwise would continue to be provided by thephotosensitive element 3. This element 3 is in a position to receivelight which has passed through the objective and which is reflected bythe tiltable mirror, so that when the latter has swung upwardly beyondthe optical axis there is no longer any impingement of light on theelement 3 from the object which is to be photographed.

The switching circuit means 12 receives from the signal-transmission 9the signal corresponding to the addition of the exposure-determiningfactors as described above. This switching circuit means 12 includes afield effect transistor 42 of high input impedance and a variableresistor 23 connected to the output terminal of the transistor 42, thisvariable resistor 23 also forming a potentiometer having a slidingcontact 24. This contact 24 forms part of a mechanism referred to belowwhich operates in a mechanical way to bring about an exposure time ofextremely short duration. The switching circuit means 12 furtherincludes a switching element 25 such as a thyristor for controlling thedeenergizing of the electromagnetic means 2, and the sliding contact 24of the variable resistor means 23 is electrically connected to thecontrol electrode of the thyristor 25.

The switch is automatically closed just before the shutter is opened,while the tiltable mirror snaps upwardly, and at this instant the chargestored in the memory capacitor 9 is insufficient to render the switchingelement 25 conductive. Therefore, the transistor 14 remains in itsconductive state to maintain the electromagnet 2 in its energizedcondition. As a result the electromagnetic means 2 holds the elementswhich are required to be released in order to permit the shutter toclose, and thus these elements are prevented from operating even beforethe shutter opens, when the electromagnetic means 2 is energized byclosing of the switch 15.

The circuitry includes an additional field effect transistor 26connected in parallel with the field effect tran sistor 42. Anindicating means 13, in the form of a suitable meter such as an ammeter,is connected to the transistor 26 in parallel with the output loadresistance 27 thereof. This indicating means 13 takes the form of anexposure meter structure in which an ammeter is utilized as theindicating instrument.

During transmission of the signal from the memory capacitor 9 to theswitching circuit means 12, the transistor 26 controls the electriccurrent which flows therethrough in accordance with the magnitude of thesignal. Thus, the transistor 26 will serve to reliably transmit thesignal stored in the capacitor 9 to the indicating means 13 in the formof a meter which is controlled in accordance with the magnitude of thesignal. This structure for giving an indication of the result of themeasurement of the light and the addition of the otherexposure-determining factors includes the transistor 42 of high inputimpedance which forms the input for the switching circuit means 12 andthe separate parallel-connected transistor 26 of high input impedance,so that the switching circuit operation with this circuitry iscompletely free of any electrical disturbance from the indicating means13 which otherwise would occur if the. parallel connection through theseparate transistor 26 were not provided. Therefore the operation of theswitching circuit means 12, on the one hand, and the indicating means13, on the other hand, never interfere with each other. The value whichis indicated by the indicating means 13 corresponds to a shutter speed,and this indicating means 13 may be provided with a scale of shutterspeeds having graduations which cooperate with the movable pointer sothat the operator can directly read from the meter 13 the exposure timewhich will be provided by the circuitry, this exposure time beingdirectly measured in seconds on the scale at the meter 13 andcorresponding to the magnitude of the signal which is transmitted to theswitching circuit means 12 by the signal-transmission means 9. Theindication given by the indicating means 13 is provided through asuitable switch which becomes closed automatically during the initialpart of the depression of the shutter-tripping plunger, before theshutter is actually tripped, so that after slight depression of theshutter-tripping plunger it is possible to measure at the meter 13factors such as the light at the object to be photographed, and theoperator may hold the shutter-tripping plunger in a partially depressedcondition in order to preliminarily see at the meter 13 the value of theshutter speed which will be provided by the circuitry if the depressionof a shutter-tripping plunger is continued to actually trip the shutter.

During the further depression of this shutter-tripping plunger thetiltable reflector is snapped upwardly in a known way, and the switch 11is automatically opened through a suitable transmission during theinitial part of the depression of the shutter-tripping plunger. Thememory capacitor 9 thus remains in its condition corresponding to thatwhich obtains just prior to opening of the switch 11. The tiltablemirror snaps upwardly and then with the completion of the depression ofthe shutter-tripping plunger the shutter opens.

ln synchronism with the opening of the shutter the switch 10 opens, andas this switch 10 opens the capacitor 9 is additionally charged throughthe logarithmic expansion circuit 8 from the voltage regulator 7. Thenthe input voltage of the switching circuit means 12 attains the level atwhich the switching circuit 12 transfers to a conductive state as thecharging of the capacitor 9 continues, and thus the switching circuit 12will suddenly transfer to a state of electrical continuity orconductivity. Therefore, the duration of the interval from the start ofthe additional charging through the logarithmic expansion circuit 8 tothe transfer of the switching circuit means 12 to the state ofelectrical conductivity corresponds to the timing signal whichdetermines the duration during which the shutter remains open, or inother words the duration of the exposure. The manner in which such atiming value is achieved is described in detail in copending applicationSer. No. 28,457, so that it is not described further.

It is possible to achieve control of relatively long exposures, forexample longer than 1/500 see, with extremely great precision throughthe operation of the is at an extremely high speed range on the order of1/ 1000 sec., for example, tends to be unstable due to factors such asthe time lag in the operation of the electromagnet 2. A mechanicalshutter control mechanism may be operated preliminarily to achieve aneffective control with extremely short exposure times in cases such asthe photographing of objects which move at high speed. Under theseconditions control of the shutter by the electrical circuitry whichincludes the switching circuit means 12 should be avoided so that thisswitching circuit means should not operate at this time. This type ofoperation is achieved by deenergizing the electromagnet 2 so that itwill release the trailing curtain and thus terminate the exposure.

For this purpose, there is provided at the switching circuit means 12 acontrol means which controls the electromagnet in order to achieve, in amechanical way, an extremely short exposure time. This control meansincludes the sliding contact 24 of the variable resistor 23 which forthis purpose assumes a position displaced along the resistor 23 to alocation where a bleeder voltage is produced at the sliding contact 24in association with thechange-over from electrical control to mechanicalcontrol. The arrangement is such that this bleeder voltage issufficiently positive and of such a magnitude that it is great enough totransfer by itself the switching element 25 to the conductive state atthe instant when the memory capacitor 9 is completely charged.

Thus, through the control achieved with a bleeder voltage resulting fromthe displacement of the contact 24 in association with the thyristor 25it is possible to achieve in a mechanical way a deenergizing of theelectromagnet 2 suitable for high speed operation where an extremelyshort exposure time is required.

During normal operation with longer exposure times, the switchingelement 25 transfers to its state of electrical conductivity and thevoltageon the anode side thereof drops sharply. A Zener diode 26 isinserted between the anode of the thyristor 25 and the base of thetransistor 14. As long as the thyristor25 is in a nonconductive state,the Zener diode 26 is in its conductive state since the Zener diode 26is provided with voltage higher than its Zener voltage as a'result ofenergizing of the Zener diode 26 from the voltage regulator 6. At theinstant when the element 25 transfers to its conductive state the Zenerdiode transfers to its nonconductive state since the input voltage tothe diode 26 will drop instantaneously at this time.

The transistor 14 transfers to its non-conductive state only underregulation of the magnitude of the control signal from the Zener diode26 which is connected to the control electrode of the transistor 14,this operation taking place without any delay due to the counterelectromotive force generated when the electromagnetic means 2 connectedin series with the switching transistor l4 and serving to initiate theshutter-closing operation is deenergized. More specifically, thistransistor 14 transfers completely to its state of electricaldiscontinuity when the control signal to the transistor 14 isinstantaneously eliminated by the Zener diode 26 according to the signalfrom the switching element 25 at the instant when the latter becomesconductive. In this way the electromagnetic means 2 becomes deenergizedso that the trailing curtain is released from the holding effect of theelectromagnetic means 2 and starts to run in order to terminate theexposure by closing the shutter.

The circuitry provides a highly effective operation of theelectromagnetic means 2. This electromagnetic means 2 which has a highpower requirement is energized by way of the switch 15 just prior toopening of the shutter. The instant when the electromagnetic means 2 isenergized is selected in such a way that the duration of operation ofthe electromagnetic means 2 is reduced to a minimum. Therefore, theswitch 15 is not closed until the final moment before opening of theshutter, so that in this way the electromagnetic means 2 will reliablyhold the trailing curtain but at the same time will be maintainedenergized for a minimum duration. Accordingly, it is important to reduceto a minimum the time lag from the instant of closure of the switch 15to activation of the electromagnetic means 2. This result is effectivelyachieved by supplying a large quantity of electricity to theelectromagnetic means 2. The battery 17 itself, however, has an internalresistance, with the result that it is difficult to provide a largequantity of electricity instantaneously. With the circuitry disclosed inFIG. 1, however, a capacitor 40 is connected through the main switch 16in parallel with the battery 17, and the capacitor 40 will have itsdischarge circuit established through the electromagnetic means 2 uponclosing of the switch 15. Thus, the capacitor 40 forms a means forsupplying to the electromagnetic means 2 power in addition to that whichis derived directly from the battery 17 upon closing of the switch 15.Prior to closing of the switch 15 the capacitor 40 is preliminarilycharged from the battery 17 through the main switch 16 which is closedprior to closing of the switch 15. Thus, the charge which has beenstored on the capacitor 40 is discharged to the electromagnetic means 2at the instant when the switch 15 closes and the electromagnetic means 2is accordingly sufficiently energized by the additional energy from thecapacitor 40 as well as the energy from the battery 17 to achieve aninstantaneous activation of the electromagnetic means 2. In this way theabove time lag is very substantially reduced.

In addition, while a DC current is supplied to the electromagnetic means2 from the battery 17, a feeble AC component is applied to the circuitwhich energizes the electromagnetic means 2 from the DC-DC converter 1by way of the-circuit which connects the battery 17 and the converter 1to each other, so that in this way a rippled direct current composed ofan AC output and the output from the battery 17 is supplied to theelectromagnetic means 2. This rippled current effectively acts upon theelectromagnetic means 2 when the transistor 14 is turned off. The rippleform of current acts so that it is possible for an electromagneticallyattractive force generated due to magnetic hysteresis of theelectromagnetic means 2, upon deenergizing thereof, to be rapidlycounteracted by the ripple current as the switching circuit means 12transfers to the electrically conductive state and the transistor 14completely transfers to the electrically non-conductive state.Accordingly, upon deenergizing of the electromagnet 2, its holdingeffect on the trailing curtain is immediately given up and shutterclosing takes place in stantaneously without any possible delay of thetype re ferred to above.

Thus, this circuitry for controlling the electromagnetic means 2 isuseful to reduce the time lag with respect to the moment when theelectromagnetic means 2 is energized as well as the time lag withrespect to the instant when the electromagnetic means 2 is deenergized,with time lags at both of these instants being reduced to a minimum soas to bring about a highly effective precision in the operation.

In the embodiment described above the memory capacitor 9 is charged withthe output from the exposuredetermining factor adding circuit 5, and theexposure time is automatically determined according to the factor oflight intensity and the additional factors added by the circuit 5. Withthe embodiment of FIG. 2, the switch 11 has the form of a change-overswitch serving to selectively connect into the circuit either thesignalsupply means formed by the circuit and the lightresponsive circuitor an additional manually operable signal-supply means formed bycomponents 30-32 and connected to the contact 11b of the change-overswitch 11 of FIG. 2. The contact 11a of this change-over switch servesto transmit to the circuitry the signals from the signal-supply meansreferred to above.

The manually operable signal-supply means 30-32 supplies a bleedervoltage output terminal 32 of the bleeder circuit 31 which is connectedto its own independent power source 30. The output terminal 32 ismovable relative to the bleeder resistance 31 so that the output voltagecan be manually determined. This manual determination of the magnitudeof this output voltage may be brought about by turning a suitable dialwhich is displaced in accordance with shutter speed graduations.

Thus, when the operator selects to manually determine the exposure time,the switch 11 will be placed in engagement with the contact 11b, and nowthe capacitor 9 is charged to the level of the bleeder output voltage ofthe manually operable signal-supply means. When the bleeder outputvoltage is that resulting from operation in accordance with a selectedshutter speed graduation, the information of signal stored in thecapacitor 9 takes a value corresponding to this graduation and theselected shutter time corresponding to the selected graduation isachieved by additional charging in precisely the same way as duringautomatic control in the manner described above. In this way it ispossible to achieve with the embodiment of FIG. 2 a manually selectedexposure time while utilizing only a minimum amount of additionalstructure with the same controls, except for the signal supply means,being used both for automatic and manual exposure time determination.

The embodiment of FIG. 3 corresponds to those described above except forthe following differences. This embodiment includes a manually operableswitch 33 for opening and closing a checking circuit means capable ofchecking the condition of the voltage. source 17. The normally openmanually operable switch 33 serves to connect-the battery 17 to aresistor 34 of the checking circuit, this resistor 34 being connected inseries with a resistor 35 which in turn is connected with a diode 36inserted in a forward direction with respect to the battery 17 whichserves as a DC power source. These components of the checking circuitmeans are connected in series between the battery 17 and the inputterminal 13a of the indicating means 13. The checking circuit meansfurther includes a thermal compensating element 37 and adjustingresistances 38 and 39 which are connected in parallel with theresistance 35, the diode 36, and the indicating meter 13 so as toachieve in this way a voltage checking circuit for determining thecondition of the battery 17 as the DC power source.

During checking of the voltage of the battery 17, the switch 33, whichnormally remains open, is manually closed. Of course, before closing theswitch 33 the main switch 16 is opened so that there will be nointerference with the checking of the condition of the battery 17 fromthe remainder of the circuitry. Closing the switch 33 initiates theenergizing of the indicating means 13 through the resistances 34 and 35and the diode 36 from the battery 17, so that the voltage of the battery1 may be reliably checked through reading this voltage which isindicated at a suitable scale of the meter 13 under regulation of thethermal compensating element 37. The diode 36 provided for checking ofthe voltage of the battery 17 as a DC power source is inserted in theforward direction with respect to the battery 17 so that the operationof the voltage checking circuit will have no influence on the operationof the indicating means 13 when the switch 33 is opened. Thus the samemeter 13 can be used for preliminarily indicating to the operator theexposure time which will be automatically achieved, as pointed outabove, as well as for battery checking purposes, without the checkingcircuit having any influence on the meter 13 when the switch 33 is open.Therefore, during measurement such as light measurement to control theelectric shutter the battery checking circuit will have no undesirableinfluence as a result of the diode 36.

Thus, the above circuitry assures a highly reliable operation byproviding the above checking circuit which enables the battery 17 to bemaintained in proper operating condition, as well as by providing amulti-source system formed by the DC-DC converter 1 and the voltageregulating means 6. and 8 in each load circuit which is likely to bethermally influenced in an undesirable manner.

What is claimed is:

1. In a camera having circuitry for automatically determining the extentto which film in the camera is exposed, said circuitry including acircuit for providing a signal according to the magnitude of theexposure aperture, the latter circuit comprising a first variableresistor means for introducing a signal according to a preselecteddiaphragm setting when using an objective which has a wide open aperturewhich is automatically stopped down to the preselected aperture justprior to exposure, secondvariable resistor means for introducing asignal according to the magnitude of the exposure aperture when using anobjective which is not automatically stopped down to a preselectedaperture, so that with the latter objective light measured after passingtherethrough is restricted by the stopped down aperture, a bypass switchmeans connected across said first variable resistor means forintroducing from said first variable resistor means a signal equal tothat introduced by said second variable resistor means when said bypassswitch means is in a closed state, said first and second variableresistor means being connected in parallel with each other and at leastone of said variable resistor means including an electrically conductiveadjustable component for determining the setting of said one variableresistor means, and switch means operatively connected with saidcomponent for selectively connecting the latter to said circuitry.

2. The combination of claim 1 and wherein a third variable resistormeans having at least one adjustable component for determining thesetting thereof is connected in parallel with said first and secondvariable resistor means for introducing a signal according to apredetermined exposure-determining factor.

3. The combination of claim 1 and wherein said circuitry includes alight-responsive means for responding to light at the object to bephotographed for introducing a signal in accordance with the lightingconditions, said change over switch meansbeing electrically connectedwith said light-responsive means.

4. The combination of claim 3 and wherein said lightresponsive meansincludes a photosensitive element for receiving light from the object tobe photographed and for responding thereto to provide an electricalquantity in accordance with the intensity of the light at the object tobe photographed, a diode connected in series with said photosensitiveelement, and said switch means being electrically connected to ajunction between said photosensitive element and said diode.

S. The combination of claim 1 and wherein both said first and saidsecond variable resistor means include electrically conductiveadjustable components for determining the settings of said first andsecond variable resistor means, said change over switch means being 14electrically connected with said components for selectively connectingone or the other of said components to said circuitry.

6. The combination of claim 2 and wherein said exposure-determiningfactor is the speed of the film which is exposed.

7. The combination of claim 5 and wherein said circuitry includes alight-responsive means for responding to light at the object to bephotographed for introducing a signal in accordance with the lightingconditions, said change over switch means being electrically connectedwith said light-responsive means.

8. The combination of claim 7 and wherein said lightresponsive meansincludes a photosensitive element for receiving light from the object tobe photographed and for responding thereto to provide an electricalquantity in accordance with the intensity of the light at the object tobe photographed, a diode connected in series with said photosensitiveelement, and said change over switch means being electrically connectedto a junction between said photosensitive element and said diode.

9. The combination of claim 1 and wherein said bypass switch means is anormally open switch means which is automatically closed when using anobjective which is not automatically stopped down.

1. In a camera having circuitry for automatically determining the extent to which film in the camera is exposed, said circuitry including a circuit for providing a signal according to the magnitude of the exposure aperture, the latter circuit comprising a first variable resistor means for introducing a signal according to a preselected diaphragm setting when using an objective which has a wide open aperture which is automatically stopped down to the preselected aperture just prior to exposure, second variable resistor means for introducing a signal according to the magnitude of the exposure aperture when using an objective which is not automatically stopped down to a preselected aperture, so that with the latter objective light measured after passing therethrough is restricted by the stopped down aperture, a bypass switch means connected across said first variable resistor means for introducing from said first variable resistor means a signal equal to that introduced by said second variable resistor means when said bypass switch means is in a closed state, said first and second variable resistor means being connected in parallel with each other and at least one of said variable resistor means including an electrically conductive adjustable component for determining the setting of said one variable resistor means, and switch means operatively connected with said component for selectively connecting the latter to said circuitry.
 2. The combination of claim 1 and wherein a third variable resistor means having at least one adjustable component for determining the setting thereof is connected in parallel with said first and second variable resistor means for introducing a signal according to a predetermined exposure-determining factor.
 3. The combination of claim 1 and wherein said circuitry includes a light-responsive means for responding to light at the object to be photographed for introducing a signal in accordance with the lighting conditions, said change over switch means being electrically connected with said light-responsive means.
 4. The combination of claim 3 anD wherein said light-responsive means includes a photosensitive element for receiving light from the object to be photographed and for responding thereto to provide an electrical quantity in accordance with the intensity of the light at the object to be photographed, a diode connected in series with said photosensitive element, and said switch means being electrically connected to a junction between said photosensitive element and said diode.
 5. The combination of claim 1 and wherein both said first and said second variable resistor means include electrically conductive adjustable components for determining the settings of said first and second variable resistor means, said change over switch means being electrically connected with said components for selectively connecting one or the other of said components to said circuitry.
 6. The combination of claim 2 and wherein said exposure-determining factor is the speed of the film which is exposed.
 7. The combination of claim 5 and wherein said circuitry includes a light-responsive means for responding to light at the object to be photographed for introducing a signal in accordance with the lighting conditions, said change over switch means being electrically connected with said light-responsive means.
 8. The combination of claim 7 and wherein said light-responsive means includes a photosensitive element for receiving light from the object to be photographed and for responding thereto to provide an electrical quantity in accordance with the intensity of the light at the object to be photographed, a diode connected in series with said photosensitive element, and said change over switch means being electrically connected to a junction between said photosensitive element and said diode.
 9. The combination of claim 1 and wherein said bypass switch means is a normally open switch means which is automatically closed when using an objective which is not automatically stopped down. 